Hello Parag
You make reference to this promotion:
https://www.sbb.ch/en/campaign/day-pass-for-2.html
The Day Pass for 2 is primarily destined for residents, to promote the resident half fare card.
This year, however, tourists are not excluded and you are welcome to use it with your Swiss Half Fare Card. It is, by the way, clearly stated on the product landing page:

Kind regards,
Roland